Enhancement of audio signals based on digital techniques

Digital signal processing can be applied to the task of subjectively improving the quality of existing recordings which are degraded by noise or distortion. An efficient method is based on a multiband filter bank which ensures flat overall response. Such a filter bank, based on complementary filters, polyphase processing, and two separate FFT´s, is presented, along with the details of its design and its relevance to psychoacoustic parameters. The filter bank allows the use of multi-band expansion techniques which effectively suppress noise components. The achieved signal enhancement is described and illustrated by audio signals. Although complex in design, the filter bank can be implemented efficiently. The design path from theory to high-level-language simulation to architecture and microcode definition, to microcode justification and to hardware is briefly described.